In the production of circuit elements, it is known to utilize photolithography to build-up structures on the surfaces of a substrate, hereinafter also referred to as a sample, utilizing the application of a photoresist or photopolymer which, upon exposure through a mask or template, can be developed to leave an opening, passage or window through which a deposit can be formed on the substrate or a surface treatment can be undertaken upon the substrate as thus revealed.
In such devices, for example MESFETs, volume characteristics of the material can be used and at times there is a need to align on the back of the sample or substrate structures with the circuit elements on the front of the sample or substrate with considerable recording accuracy. It is possible, utilizing conventional photolithography, to provide structures having circuit elements on both the rear and front surfaces of a substrate which are aligned with accuracies of the order of .+-.1 micrometer.